The present invention relates to displacement indicators and, more particularly, to opti-mechanical indicators by means of which very small displacements or movements of one member relative to another are indicated via a change in intensity or color of an indicator.
There are many situations where the indication of very small distances or displacements is needed. Prior to the present invention, precision gauging instruments, such as micrometers, dial indicators, feeler gauges, and electronic indicators, were required to accomplish the precise setting or indicating of minute displacements in the order of 0.0001 inch (2.5.mu.m). It would obviously be preferable, especially in the field, if such instruments or gauges were not needed, and if the adjustments could be set visually to within acceptable limits with the aid of a built-in indicating device.
One advantageous utilization of the indicators of the present invention is as a stress-strain indicator in applications such as described in my U.S. Pat. No. 3,602,186 and in U.S. Pat. No. 3,799,108 to Mosow. The utilization of such strain indicators more fully than at present has been hindered by such factors as cost, and complexity in design and manufacture. The Mosow patent discusses various problems associated with producing the indicator of my earlier patent. In an effort to overcome such problems, Mosow proposes a complex manufacturing and assembly process which includes making subassemblies in which the indicator fluid is encapsulated with an indicator area attached to a pin member, prior to uniting with a threaded bolt subassembly.